Data access control apparatus, data access control method, controller, and computer program

ABSTRACT

A magnetic head accesses sectors of one track in the order starting with a sector where the magnetic head is put into an on-track state. A seek start timing is reliably determined by accessing on a track by track basis with an uncertain process of a read-ahead operation eliminated. A search time is eliminated by accessing any sector within one track. As a result, the number of seeks is minimized and access time is reduced. A sector format is used to perform an access operation on a track by track basis. In this arrangement, each of seek time and search time is reduced during a random access time and a data transmission speed of a disk drive is assured.

TECHNICAL FIELD

The present invention relates to a data access control apparatus, a dataaccess control method, a controller and a computer program, for arandom-access recording medium and, in particular, to a data accesscontrol apparatus, a data access control method, a controller and acomputer program, for a disk-type recording medium such as a hard diskwhich a magnetic head scans to write data to or read data from.

More specifically, the present invention relates to a data accesscontrol apparatus, a data access control method, a controller and acomputer program for reducing access time to a desired data storagelocation and, in particular, to a data access control apparatus, a dataaccess control method, a controller and a computer program, free from adelay in a seek startup due to a useless read-ahead operation withoutresulting in a search time.

BACKGROUND ART

With the advance of information technology such as informationprocessing and information communications, information produced andedited in the past requires reutilization and information storagetechnology becomes more important. Information recording apparatusesusing a variety of media such as a magnetic tape and a magnetic diskhave been developed and in widespread use.

Among them, a hard-disk drive (HDD) is an auxiliary storage device of amagnetic recording method. A plurality of magnetic media as a recordingmedium are housed in a drive unit, and is rotated by a motor at a highspeed. The medium is coated with a magnetic material such as iron oxideor cobalt chromium alloy using a plating technique or a thin-filmforming technique. A magnetic head radially scans across the surface ofthe rotating medium and causes a magnetization in response to data onthe medium to write the data, or reads the data written on the disk.

The hard disks are already in widespread use. The hard disk as astandard external storage device of a personal computer stores adiversity of computer softwares including an operating system (OS) forstarting up the computer and application software programs, or storesreproduced and edited files. The hard disk drive is connected to thecomputer main unit through an IDE (Integrated Drive Electronics) or aSCSI (Small Computer System Interface), and the storage space of thehard disk is typically managed by a file system, such as an FAT (FileAllocation Table), which is a subsystem of the host operating system.

The hard disk drives have currently a large storage capacity. With largestorage capacity, the hard disk drive is used not only as a conventionalcomputer auxiliary recording device but also as a hard disk recorderthat stores audio-vidual contents broadcast and received. With theapplication field thereof expanded, the hard disk is used to record avariety of contents.

A physical format method of the hard disk and a data read and writeoperation of the hard disk, as a computer auxiliary storage device, arenow considered.

The hard disk has numerous concentric “tracks” as segments for recordingdata. For example, track numbers 0, 1, . . . are assigned the outer mosttrack to inner tracks. Generally, the larger the number of tracks on thesurface of the hard disk, the larger the storage capacity of the medium.

Each track is divided into “sectors”, each sector serving a unit ofrecording. Standard read and write operations on the disk are performedon a per sector basis. The size of sector is different from medium tomedium. The sector of the hard disk has typically a size of 512 bytes.Taking into consideration the utilization of the medium, outer trackshaving longer track length have more sectors along to make the recordingdensity on the track substantially uniform. This method is called a“zone bit recording” method.

The zone bit recording provides a substantially uniform recordingdensity on the tracks while resulting in non-uniformity in datatransmission speed from track to track (inner tracks presents slowerdata transmission speeds).

FIG. 26 diagrammatically illustrates the structure of the recordingsurface of the hard disk. As shown, when the hard disk drive performs anaccess operation, a seek operation for seeking a next track must also beperformed in the case of the longest one track access.

In a hard disk drive having a plurality of media stacked in a coaxialmanner, tracks of the same track number of the media are cylindricallyarranged, and are thus referred to as a “cylinder.” Each cylinder islabeled the same number as the track number. For example, from theoutermost side, cylinder 0, cylinder 1, . . . As a result, the track isidentified by the cylinder number and a head number corresponding to themedium. A plurality of heads, each interposed between the media, arealways integrally driven, moving from cylinder to cylinder.

A CHS mode is available as a method of addressing a target sector. TheCHS mode is an addressing method that accesses desired data bydesignating a PBA (Physical Block Address) on the disk in the order of C(cylinder), H (head), and S (sector).

The CHS method is subject to a limitation in CHS parameters designatedby a computer main unit which functions as a host to the hard diskdrive. The CHS is unable to cope with a large-capacity hard disk. Forthis reason, an LBA (Logical Block Address) mode is employed. In thismode, the cylinder number, the head number, and the sector number (CHS)are expressed by a logical serial number LBA. The LBA starts with zero.

When data is read from or written to the medium in the conventional harddisk drive, the magnetic head radially scans across the disk surface toreach the track having a target sector. This action is called a “seek”operation of the magnetic head. To reach the target sector on the track,the media rotate until the target sector comes right beneath themagnetic head. This is called a “search.”

As the storage capacity of the disk becomes large, a track density ofthe disk increases, and a track width becomes narrow. To write data toand read data from the disk with precision, a high positioning accuracyis required of the magnetic head. A servo technique to continuouslyalign the position of the magnetic head at the center of the track isused. A signal called a “servo pattern” is written at regular intervalson each track. The drive checks to see if the magnetic head is alignedat the center of the track (when the magnetic head passes over the servoarea present on the data surface of the disk, the signal of the servopattern is integrated to determine whether the magnetic head is ontrack). The servo pattern is written onto the hard disk with highprecision when the hard disk drive is manufactured. FIG. 27 illustratesthe servo area of the track where the servo pattern is written. Writtenon the servo area are a signal for positioning the head, a cylindernumber, a head number, a servo number, etc.

Many conventional hard disk drives are associated with an interface suchas an IDE or a SCSI for connection with a computer. In a basic diskdrive control, the host computer designates a start address and thenumber of sectors using a command set defined by the interface.

The hard disk drive accesses sectors starting a sector designated by theaddress, and then continues accessing while generating a sequence forperforming a read-ahead operation by predicting a sector to be accessedlater.

The read-ahead operation is based on the assumption that consecutiveaddresses are assigned a series of data. Typically, consecutiveaddresses are present in consecutive head numbers or consecutive tracknumbers.

For example, when a large amount of data such as video data iscontinuously written on the media, the read-ahead operation effectivelyworks during a read operation.

If the fragmentation of the storage area is very much in progress with alarge amount of data fragmented into small pieces of data and dispersedat a plurality of locations, the read-ahead operation is not successful,designating different data during the read operation. Such anunsuccessful read-ahead operation occurs because the hard disk driveside fails to learn the structure of files handled by a host (computermain unit) requesting data read and data write.

If a prediction provided by the read-ahead operation is erroneousbecause of a new access request from the host, the hard disk drive seeksa track containing an address having requested data present therewithin,and waits subsequent to the completion of tracking until a targetaddress becomes accessible. There, a seek time and a search time occur.

The read-ahead data may be stored as long as the capacity of a databuffer permits. If the prediction is erroneous consecutively orintermittently, unused old data is successively discarded in the orderof old data to young data. During the read-ahead operation, the seekoperation is not initiated.

The disk is subject to the seek time, the search time, the loss of timedue to a delay of seek start as a result of the read-ahead operation,and data missing due to useless read-ahead operation.

The number of revolutions of the disk is increased to reduce the seektime and the search time in the ordinary disk drive. Since there is noregular pattern in the amount and structure of data used in the hostsuch as the computer, improvements by means of the access method areimpossible. Such a disk access method presents problems in powerconsumption and storage capacity.

As disclosed in Japanese Unexamined Patent Application Publication No.58-33767, the use of a data buffer improves an access operation during aread operation. A read operation starts at a position which is not astart sector to which an access is requested.

As disclosed in a paper entitled “Track-aligned Extents: Matching AccessPatterns to Disk Drive Characteristics” authored by Jiri Schindler et.al., Conference on FAST Jan. 28-30, 2002, Monterey, Calif., accessimprovements are made by allowing a host to access a disk on a track bytrack basis.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide an excellent dataaccess control apparatus, a data access control method, a controller,and a computer program for appropriately reading data from and writingdata to a magnetic disk as a medium by allowing the magnetic head toscan the magnetic disk.

It is another object of the present invention to provide an excellentdata access control apparatus, a data access control method, acontroller, and a computer program for reducing an access time to adesired data storage location.

It is yet another object of the present invention to provide anexcellent data access control apparatus, a data access control method, acontroller, and a computer program, free from a search time and freefrom a delay in a seek startup due to a useless read-ahead operation.

It is a further object of the present invention to provide an excellentdata access control apparatus, a data access control method, acontroller, and a computer program, for reducing a seek time and asearch time during a random access by improving a data structure on adisk as a medium and a disk access method.

The present invention has been developed in view of these and otherdrawbacks. The present invention in a first aspect relates to a dataaccess control apparatus or a data access control method for controllingan access to a disk-type recording medium, which includes a pluralityconcentric tracks with each track divided into a plurality of sectors,and includes seek means or a seek step for seeking a target track, anddata access means or a data access step for accessing the sectors of thesought track in the order starting with a start sector which becomesaccessible on the sought track.

The data access control apparatus or the data access control method inthe first aspect of the present invention may be applied to a magneticdisk type recording medium such as a hard disk drive. In this case, theplurality of substantially concentric tracks are provided on the surfaceof the disk, and each track is divided into a plurality sectors. Themagnetic head is radially moved across the rotating disk to seek atarget track, and accesses a sector on the track in the direction ofrotation.

Conventional hard disk drives must wait in search time until an accessrequested start sector on the track arrives at the magnetic head. Aread-ahead operation is performed to predict a sector to which an accessis expected. If a fragmentation is very much in progress on the disk,the read-ahead operation becomes useless.

The data access control apparatus or the data access control method inthe first aspect of the present invention accesses the sectors of onetrack from the sector where the magnetic head is on-track. Morespecifically, handling one track as a unit of access eliminates anuncertain process of the read-ahead operation, reliably determining theseek start timing. Since an access operation may start with any sectoron the track, read and write operations are performed at any headposition immediately subsequent to the seek operation. A search time isthus eliminated. The number of seeks is minimized and the access time isreduced.

In the conventional hard disks, a data access operation is performedbased on absolute position addresses assigned beforehand the tracks andthe sectors. In contrast, the data access control apparatus or the dataaccess control method in the first aspect of the present inventionsuccessively allocates relative position addresses to the sectors on thetrack in the order starting with the start sector where a data accessoperation has started during a write access.

In accordance with the present invention, a write requesting source (ahost apparatus such as a computer connected to the hard disk drive) neednot be conscious of a write destination address on the disk. On theother hand, during a read access, data read from the sector on the trackmay be repositioned in accordance with the relative position addresseson a buffer memory. Regardless of the position of the start sector inthe access operation, original data is reconstructed. The storage areaof the disk is efficiently utilized by using the relative positionaddresses that are short in size.

The data access control apparatus or the data access control method inthe first aspect of the present invention may further include errorcorrection means or an error correction step for generating an errorcorrection code for error correcting data and of error correcting thedata in accordance with the error correction code.

In this arrangement, the relative position address, the data body, andthe error correction code which covers the relative position address,the data body, and the error correction code within an error correctionrange may be written on each sector. Alternatively, the data body, andthe error correction code which covers the relative position address,the data body, and the error correction code within an error correctionrange thereof may be written on each sector.

In the latter case, during a read access, the data read from each sectoris error corrected by the error correction means to reproduce therelative position address. The data is then reconstructed based on thereproduced relative position address. By removing the relative positionfrom the write data, the storage area of the disk is efficientlyutilized.

Servo areas are arranged at regular intervals on the track of the harddisk. With the servo areas, a servo control is performed to keep themagnetic head aligned at the center of the track.

If the sector has a fixed length, each of several sectors straddles theservo area. In such a case, the data access means or the data accessstep treats, as an accessible start sector, a sector which is providedwithout straddling the servo area on the sought track.

If each sector has a variable length, none of the sectors is designed tostraddle the servo area. In such a case, the data access means or thedata access step treats, as an accessible start sector, a sector whichis immediately subsequent to a servo area on the sought track.

The storage area of the disk-type recording medium may be divided intotwo partitions. In one partition, when the sectors of one track areaccessed, the access operation starts at a start sector that becomesaccessible. In the other partition, the access operation is performedbased on the absolute position addresses of the track and the sector asin the conventional art.

The present invention in a second aspect relates to a data accesscontrol apparatus or a data access control method for controlling anaccess to a disk-type recording medium, which includes a pluralitysubstantially concentric tracks with each track divided into a pluralityof sectors, and includes seek means or a seek step for seeking a targettrack, data access means or a data access step for accessing the sectorson the sought track, determining means or a determining step fordetermining the relationship between a seek time and a seek distance ofthe track to be accessed by the data access means or in the data accessstep, and data write control means or a data write control step forallocating logical block addresses to the sectors during data writing sothat the seek time covers a plurality of track seeks within a range thatthe seek time does not exceed search time taking into consideration therelationship between the seek time and the seek distance.

The data access control apparatus or the data access control method inthe second aspect of the present invention allocates the logical blockaddresses to the sectors so that the seek time covers a plurality oftrack seeks within a range that the seek time does not exceed searchtime.

From a servo frame which has undergone the writing of one track, a seekis performed not exceeding mean search time, and that time is referredto as a track skew. When data is written on the disk, the consecutivelogical block addresses are repositioned on the disk taking intoconsideration the track skew. When a continuous access straddling aplurality of tracks is performed, data transmission speed is madeuniform.

Japanese Unexamined Patent Application Publication No. 9-185864discloses a technique in which a skew reducing a search time at anaverage distance of travel of the head is determined, a recordingposition is determined based on the skew, and an access request isscheduled. The determination of the track skew may employ a methodsimilar to this.

When the data is written on the disk, the consecutive block addressesare successively allocated to the tracks within a range where the seektime or the track skew does not exceeds a predetermined value. Even if aseek operation is performed to any track, the seek time to the track ismade uniformed during a continuous access operation, and the search timeis minimized.

The determining means or the determining step for determining therelationship between the seek time and the seek distance may perform aseek operation on a disk drive with the seek distance changing, andmeasures the seek time thereby determining the relationship between theseek time and the seek distance.

The present invention in a third aspect relates to a data access controlapparatus for controlling an access to a disk-type recording medium,which includes a plurality substantially concentric tracks with eachtrack divided into a plurality of sectors, and includes seek means or aseek step for seeking a target track, data access means or a data accessstep for performing an access operation on the sought track, and datawrite control means or a data write control step for treating, as anaccess start sector, a sector immediately subsequent to an on-trackservo area during data writing.

In the data access control apparatus or the data access control methodin the third aspect of the present invention, the combination of the LBAand the CHS is not singular, and the sector is arranged at anappropriate position taking into consideration the individual differenceand the operational status of the disk drive.

When the magnetic head shifts by M tracks to seek a target track from animmediately prior track in a write operation, the physical sectorposition to start access on the target track is off by a skew withrespect to the immediately prior track through the seeking by M tracks.This means that a factor such as the seek distance from the immediatelyprior track changes a track format during a write.

The present invention in a fourth aspect relates to a data accesscontrol apparatus or a data access control method for controlling anaccess to a disk-type recording medium, which includes a pluralitysubstantially concentric tracks with each track divided into a pluralityof sectors, and includes seek means or a seek step for seeking a targettrack, data access means or a data access step for accessing the sectorsof the sought track in the order starting with a start sector whichbecomes accessible on the sought track, command receiving means or acommand receiving step for receiving a write request command, datareceiving means or a data receiving step for receiving write data, acache or a step for temporarily storing the received data, and datawrite control means or a data write control step for controlling a writeoperation of writing data onto the recording medium, wherein the datawrite control means or the data write control step causes the dataaccess means or the data access step to initiate a write access of onetrack if the area of the data requested to write is continuous from thedata stored in the cache, and if an access range exceeds one track.

Since the data access control apparatus and the data access controlmethod in accordance with the present invention performs an accessoperation on a per track basis, the number of sectors per track is notdivisible by the unit of access. A remainder empty area, namely, a“blank area” is caused. Data, such as a still image or an ordinarycomputer file, which requires no real-time handling, may be stored inthe blank area.

If an access requesting a continuous recording to the blank areas, whichare not used as consecutive areas, is performed in the data accesscontrol apparatus and the data access control method in the fourthaspect of the present invention, the hard disk drive reports to the hostthat the blank area is usable, and to the host a start logical blockaddress expecting a next access. The hard disk drive thus expects thatthe next write access starts at the reported track.

The data write control means or the data write control step may writedata in response to a second issue of the same write request command ifthe area of the data requested to write is not continuous from the datastored in the cache. More specifically, if the same write request isperformed for the second time, the host is determined to be incompatiblewith the hard disk drive in the fourth aspect of the present invention,and a data write operation similar to the one performed in theconventional hard disk drive is thus performed.

The data write control means may report to a write requesting source anarea expecting a next access if the area of the data requested to writeis not continuous from the data stored in the cache and if the writedata fails to fall within the area of the data requested to write.

The present invention in a fifth aspect relates to a computer programdescribed to cause a computer system to control an access to a disk-typerecording medium, which includes a plurality substantially concentrictracks with each track divided into a plurality of sectors. The computerprogram includes a seek step for seeking a target track, and

an access step for accessing sectors of one track in the order startingwith a start sector which becomes accessible on the sought track.

The present invention in a sixth aspect relates to a computer programdescribed to cause a computer system to control an access to a disk-typerecording medium, which includes a plurality substantially concentrictracks with each track divided into a plurality of sectors. The computerprogram includes a seek step of seeking a target track, an access stepof accessing the data on the sought track, a determining step ofdetermining the relationship between a seek distance and a seek time ofthe track, and a data write control step of allocating logical blockaddresses to the sector during data writing so that the seek time coversa plurality of track seeks within a range that the seek time does notexceed search time taking into consideration the relationship betweenthe seek time and the seek distance.

The present invention in a seventh aspect relates to a computer programdescribed to cause a computer system to control an access to a disk-typerecording medium, which includes a plurality substantially concentrictracks with each track divided into a plurality of sectors. The computerprogram includes a seek step of seeking a target track, an access stepof accessing data on the sought track, and a data write control step oftreating, as an access start sector, a sector immediately subsequent toan on-track servo area during data writing.

The present invention in an eighth aspect relates to a computer programdescribed to cause a computer system to control an access to a disk-typerecording medium, which includes a plurality substantially concentrictracks with each track divided into a plurality of sectors. The computerprogram includes a command receiving step of receiving a write requestcommand, a data receiving step of receiving write data, a storing stepof temporarily storing the received data in a cache, and a data writecontrol step of controlling a write operation of writing data to therecording medium, wherein the data write control step includes startinga write access command for one track if the area of the data requestedto write is continuous from the data stored in the cache, and if anaccess range exceeds one track.

The computer programs in the fifth through eighth aspects of the presentinvention are computer readable programs described to perform apredetermined process on a computer. More specifically, by installingthe computer programs in the fifth through eighth aspects of the presentinvention in a computer system, the computer system functions incooperation with the computer programs, thereby providing the sameadvantages as the data access control apparatus and the data accesscontrol method in accordance with the first through fourth aspects ofthe present invention.

Theses and other objects, features, and advantages of the presentinvention will become apparent after considering the followingdescription of the embodiments of the present invention and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 diagrammatically illustrates the entire structure of a hard diskdrive 10 in accordance with one embodiment of the present invention.

FIG. 2 illustrates an example of a sector format in accordance with oneembodiment of the present invention.

FIG. 3 illustrates another example of the sector format in accordancewith one embodiment of the present invention.

FIG. 4 illustrates one example of a track format using the sectorformat.

FIG. 5 illustrates another example of the track format using the sectorformat.

FIG. 6 illustrates a communication example in which data is written inresponse to a command from a host to which a hard disk drive 10 of oneembodiment of the present invention is connected through an interface17.

FIG. 7 illustrates a communication example in which data is read inresponse to a command from a host 50 to which the hard disk drive 10 ofone embodiment of the present invention is connected through theinterface 17.

FIG. 8 illustrates an internal structure of a hard disk controller 13.

FIG. 9 illustrates an operational sequence of a disk formatter 13 whichwrites data in the hard disk drive 10 in accordance with one embodimentof the present invention.

FIG. 10 illustrates an operational sequence of the disk formatter 13which writes data in the hard disk drive 10 in accordance with oneembodiment of the present invention.

FIG. 11 illustrates an operational sequence of the hard disk drive 10 inread and write operations, in which CPU 11 acquires a track number of aseek destination.

FIG. 12 illustrates an operational sequence of the hard disk drive 10 inread and write operations, in which a host controller 33 acquires atrack number of a seek destination.

FIG. 13 illustrates partitions of a storage area of a disk, wherein inone partition, the hard disk drive accesses sectors of one trackstarting with a start sector that becomes accessible, and in the otherpartition, the hard disk drive accesses sectors based on absoluteposition addresses of the track and sector as in a conventional manner.

FIG. 14 illustrates the relationship between a seek distance and a seektime.

FIG. 15 illustrates the relationship between a seek distance, a seektime, and a search time.

FIG. 16 illustrates the concept of the operation of continuous accesswherein the logical block address is allocated in accordance with thepresent invention.

FIG. 17 illustrates an access operation in the seeking of the track inone embodiment of the present invention.

FIG. 18 illustrates a sector range on the track and a start position ofa sector address.

FIG. 19 illustrates a write process performed in response to a writeaccess request not exceeding the number of sectors of one track.

FIG. 20 illustrates a process performed in response to a write accessfor data of a small amount such as one other than video data wherein ablank area is registered as an unused area in a file system managed bythe host.

FIG. 21 illustrates a flow of a process performed in response to a writeaccess request for data of a small amount such as one other than videodata.

FIG. 22 illustrates a data write operation performed in response to awrite request for data of a large amount in a blank area.

FIG. 23 illustrates a flow of a process of continuous accesses for dataof a large amount such as video data.

FIG. 24 is a flow diagram of a command reception process on the harddisk drive.

FIG. 25 is a flow diagram of a seek operation.

FIG. 26 diagrammatically illustrates a (conventional) structure of ahard disk.

FIG. 27 diagrammatically illustrates a (conventional) structure of onetrack.

FIG. 28 illustrates a (conventional) allocation method of logical blockaddresses to the disk from the outermost track to inner tracks.

FIG. 29 illustrates a (conventional) operation of continuous access inwhich the logical block addresses are allocated to the disk from theoutermost track to inner tracks.

FIG. 30 illustrates the relationship between a skewing and a search timein a four-track seek.

FIG. 31 illustrates an access operation in a conventional one trackseek.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention are discussed with reference tothe drawings.

A. First Embodiment

FIG. 1 diagrammatically illustrates the entire structure of a hard diskdrive 10 in accordance with a first embodiment of the present invention.

As shown, the hard disk drive 10 includes a CPU (Central ProcessingUnit) 11, a ROM (Read-Only Memory) 12, a disk controller 13, a bufferRAM 14, a data read/write controller 15, and a servo controller 16.

The CPU 11 executes control codes stored in the ROM 12, therebygenerally controlling the operation of the drive 10.

The hard disk controller 13 receives commands from a host (not shown) towhich the hard disk controller 13 is connected through an interface 17.The CPU 11 processes the commands, thereby instructing hardware such asthe data read/write controller 15 and the servo controller 16 to operateaccordingly.

Write data received from the host through the interface 17, and dataread from a disk 21 and to be handed over to the host are temporarilystored in the buffer RAM 14.

The data read/write controller 15 performs data read and data writeoperations through a magnetic head 22, which scans across the surface ofthe magnetic disk 21 as a recording medium, and a modulation process ofthe write date, and a demodulation process of the read data.

The servo controller 16 drives, in synchronization, a voice coil motor(VCM) 23 for moving an arm bearing the magnetic head 22, and a spindlemotor (SPM) 24 for rotating the magnetic disk, thereby controlling themagnetic head 22 to reach a desired area on a target track of themagnetic disk 21. Furthermore, the servo controller 16 places themagnetic head 22 to a predetermined position in accordance with a servopattern (as already discussed) on the magnetic disk 21 in a seekoperation.

A large number of concentric tracks, each being a segment for recordingdata, is provided on the magnetic disk 21. Track numbers 0, 1, . . . areassigned the tracks of the magnetic disk 21 from the outermost track tothe inner tracks. Each track is divided into a plurality of sectors, andone sector is a minimum unit handled in data reading and data writing.

Each sector has a fixed amount of data of 512 bytes. In addition to thebody of data, header information and error correction codes arerecorded.

The hard disk drive 10 employs a ZBR (Zone Bit Recording) method, inwhich the number of sectors per circle becomes larger as it is radiallyaway from the center of the disk. More specifically, the number ofsectors per track is not uniform over the entire magnetic disk 21, andthe magnetic disk 21 is divided into a plurality of zones in a radialdirection. The number of sectors remains unchanged in the same zone.

If the zone bit recording method is adopted, the data transmission speedbecomes non-uniform from track to track (the data transmission speedbecomes lower as the head radially inwardly goes) while the recordingdensity is substantially uniform from track to track.

A plurality of magnetic disks (platters) are stacked along a coaxialaxis in the drive unit, although they are not shown. The tracks havingthe same track number of the magnetic disks (cylinder) are arrangedcylindrically, and the cylinder is designated by a cylinder numberidentical to the corresponding track number.

In the hard disk drive 10 of the present invention, one track accessoperation starts from a sector with the magnetic head 22 on-track. Thesector numbers of the same track are not fixed, and are represented by arelative position. The access operation can start at any sector of thetrack. More specifically, handling one track as a step of accesseliminates the need for performing a process based on an uncertainfactor such as a read-ahead operation. The timing of seek start isreliably determined. By performing the access operation from any sectorof the one track, a search time is eliminated. The number of seeks isminimized, and the access time is reduced.

To write data onto a predetermined track, a sector is provided with arelative position starting from a sector with which the access operationhas started.

To read data, the data is read from the sector with which the accessoperation has started, and is expanded over the buffer RAM 14 inaccordance with the relative position addresses. For this reason, theread operation may start at any sector.

Since the magnetic disk 21 is formatted as described above, the searchtime is not required. As a result, the access time to the desired sectoron the magnetic disk 21 is reduced.

FIG. 2 diagrammatically illustrates an example of a sector format usedin the magnetic disk 21 in the hard disk drive 10 in accordance with thefirst embodiment of the present invention.

As shown, each sector includes relative position data representing arelative position of each sector on the track, the body of data, and anECC (Error Correction Code) for performing an error correction on theentire area of the sector. The entire area is an error correction rangeand a recording range.

Typically, each sector contains a ID field for recording the address ofthe sector. The size of the ID field is reduced by recording therelative position rather than the absolute position. The size of thefield available to record the data body in the sector is enlargedaccordingly, and the storage area of the sector is efficiently utilized.

When data is written onto a track, a relative position from the sectorwith which the access operation has started is assigned a sector. Therelative position and the ECC data from original record data are thusgenerated. The relative position, the data body, and the ECC data arerespectively recorded onto a relative position field, a data field, andan ECC field of the corresponding sector. Since the write operationstarts at the sector with the access operation has started, no search isrequired.

A read operation starts at the sector with which the access operationhas started on the track, and based on the sector position acquired fromthe relative position field, a storage location in the buffer RAM 14 isdetermined. No matter where a data read operation starts at any sector,the data is repositioned in accordance with the relative position on thebuffer RAM 14. The data stored on the track is reconstructed in theoriginal order. Since the read operation starts at the sector with whichthe access operation has started, there no need for searching for thesector.

FIG. 3 diagrammatically illustrates another example of a sector formatused in the magnetic disk 21 in the hard disk drive 10 in accordancewith the first embodiment of the present invention.

In this case as well, each sector includes relative position datarepresenting a relative position of each sector on the track, the bodyof data, and an ECC (Error Correction Code) for performing an errorcorrection on the entire area of the sector. The entire area is an errorcorrection range, but the relative position field is not contained in arecording range unlike the case shown in FIG. 2. With the relativeposition field excluded, the size of the field available to record thedata body in the sector becomes larger than the above-referencedarrangement, and the storage area of the sector is more efficientlyutilized.

When data is written onto a track, a relative position from the sectorwith which the access operation has started is assigned a sector. Therelative position and the ECC data from original record data are thusgenerated. Only both the record data and the ECC data are recording onthe sectors. Since the write operation starts at the sector with theaccess operation has started, no search is required.

A read operation starts at the sector with which the access operationhas started on the track, and an error correction is performed using theECC. The relative position, which has not been written onto the sector,is reproduced. Based on the relative position, a storage location in thebuffer RAM 14 is determined. No matter where the read operation startsat any sector, the data stored on the track is reconstructed in theoriginal order on the buffer RAM 14. Since the read operation starts atthe sector at which the access operation has started, there no need forsearching for the sector.

FIG. 4 illustrates one example of a track format using the sectorformats show in FIG. 2 and FIG. 3.

Servo areas, each having a servo pattern, are arranged at regularintervals to perform a servo control to keep the magnetic head alignedat the center of the track (as already discussed). When the head passesover the servo area present on the data surface of the disk and aresulting servo pattern signal is integrated, the hard disk drive 10determines whether or not the head is on-track. Written onto the servoarea are a signal for positioning the head, the cylinder number, thehead number, the servo number, etc.

In the track format shown in FIG. 4, the sector has a fixed length, andeach of several sectors straddles the servo area. An accessible startsector is a first sector recorded without straddling the servo areaafter a seek operation to a target track is performed.

The hard disk drive 10 of the first embodiment of the present inventionaccesses one track from the sector where the magnetic head 22 ison-track. More specifically, the access operation is carried out on aper track basis, and where to place the absolute position of the startsector with which the access operation starts on the track is notimportant. The access operation is performed immediately subsequent tothe next servo area to place priority on an access speed.

FIG. 5 illustrates another example of the track format using the sectorformats illustrated in FIG. 2 and FIG. 3.

As shown, the sector has a variable length in the track format. Eachsector is designed not to straddle the servo area. An accessible startsector is a first sector immediately subsequent to the servo area thehead has passed after the seek operation to the target track.

Since the on-track timing of the head during the data reading isdifferent from the on-track timing of the head during the data writing(because an on-track detection is broad in response and because thetiming changes depending on an access sequence), the read operationcannot be performed in the order according to which the write operationhas been performed. To read data at the same timing with any servo areaat the beginning, the conditions of all servo areas are preferablyequalized. The sector length is thus set to be variable as shown in FIG.5.

FIG. 6 illustrates a communication example in which data is written inresponse to a command from the host 50 to which the hard disk drive 10of the first embodiment of the present invention is connected throughthe interface 17.

The host 50 issues a data write command to the hard disk drive 10. Inresponse, the hard disk drive 10 returns an address area that minimizesthe seek time in a current access sequence.

Upon receiving the reply from the hard disk drive 10, the host 50transfers a data content as large as the designated size of the addressarea (such as the number of bytes and the number of sectors). The harddisk drive 10 writes the received data content on a track by trackbasis.

As described above, if the relative position information is allocated tothe sectors with reference to the access start sector on the trackduring the write operation, the host 50 neither need to be conscious ofa specific write location such as the cylinder number, the head number,the sector number during the write operation, and nor need to designatethese numbers.

The address area the hard disk drive 10 notifies the host 50 of may beas simple as a content number that identifies a content, the writing ofwhich is requested by the host. The hard disk drive 10 prepares aconversion table between the content number and the physical storagelocation on the magnetic disk 21. Since the disk access is performed ona track by track basis in the first embodiment of the present invention,the conversion table of the content number is shown as below.

TABLE 1 Content No. Track No. Head No. 1  0-99 0 2 100-129 0 3 200-249 04 130-199 0 5 300-399 0 . . . . . . . . . 9 470-499 0 Unused — — Unused— — Unused — — . . . . . . . . . Unused 500-999 0 Unused  0-999 1

It should be noted that the conversion table does not list the sectornumber of the CHS method. In the above addressing structure that therelative position information is relatively allocated to the sectorswith respect to the access start sector on the track during the writing,the data is repositioned based on the relative position information ofthe sector during the read operation regardless of the access startsector on the track. It is therefore unnecessary to designate the accessstart sector in the conversion table.

The conversion table is written onto the buffer RAM 14. The writing ofthe conversion table is performed under the control of software executedby the hard disk controller 13 or the CPU 11 at the moment the host 50receives the write data.

FIG. 7 illustrates a communication example in which data is read inresponse to a command from the host 50 to which the hard disk drive 10of the first embodiment of the present invention is connected throughthe interface 17.

The host 50 issues a data read command to the hard disk drive 10. Thedata read command designates a content number of a target content.

In response, the hard disk drive 10 identifies a target track from theconversion table (see Table 1) in accordance with the content number,and performs a seek operation to the magnetic head 22. The hard diskdrive 10 transfers the data on the magnetic disk 21 in accordance withthe sequence in the address area corresponding to the data writeoperation.

During the data read request, the host 50 simply designates a desiredcontent number, and does not need to be conscious of a specific location(PBA) such as a cylinder number, a head number, a sector number, etc.

As described above, the hard disk drive 10 of the first embodimentaccesses one track from a sector where the magnetic head 22 is alignedon-tack. Handling one track as a unit of access, an uncertain process ofread-ahead is eliminated and the timing of the seek start is reliablydetermined. Since the access operation may be performed from any sectoron the track, the read and write operations are performed from any headposition immediately subsequent to the seek operation. The search timeis thus eliminated. The number of seeks is minimized, and the accesstime is reduced.

Such a disk access operation is carried out when the hard diskcontroller 13 instructs the data read/write controller 15 and the servocontroller 16 to operate in hardware operation in response to thecommand process result provided by the CPU 11, or when the CPU 11directly instructs the data read/write controller 15 and the servocontroller 16 to operate in hardware operation.

FIG. 8 illustrates an internal structure of the hard disk controller 13.In response to the command process result provided by the CPU 11, thehard disk controller 13 instructs the data read/write controller 15 andthe servo controller 16 to operate in hardware operations.

As shown, the hard disk controller 13 includes a microprocessorinterface 31, a clock controller 32, a host controller 33, a servocontroller 34, an ECC controller 35, a disk formatter 36, and a buffercontroller 37.

The microprocessor interface 31, serving as a connection interface ofthe CPU 11 and the ROM 12, transfers commands from the host, andreceives the command process result from the CPU 11.

The clock controller 32 supplies blocks in the disk controller withoperation clocks.

The host controller 33 communicates with the host through the interface17 which is connected thereto. Upon receiving the write data from thehost, the host controller 33 write the conversion table (see table 1).In this embodiment, the address of the access area is not designated bythe host.

The servo controller 34 controls the operation of the voice coil motor(VCM) 23 for moving an arm bearing the magnetic head 22, and a spindlecoil motor (SPM) 24 which rotates the magnetic disk, thereby readingservo information from a servo pattern on the magnetic disk 21 using themagnetic head 22, and performing servo control in a seek operation toreach a target track.

The ECC controller 35 performs error correction on data (sector data)temporarily stored in the buffer RAM 14. More specifically, when thedata is written onto the magnetic disk 21, the ECC controller 35generates the ECC of the write data and adds the ECC to the write data.When the data is read from the magnetic disk 21, the ECC controller 35performs error correction using the ECC code attached to the data readfrom the magnetic disk 21, and reproduces the relative position (refersto the foregoing discussion and FIG. 3). The ECC controller iscompatible with any sector length.

The disk formatter 36 successively writes the data of the buffer RAM 14on the track of the magnetic disk 21, or conversely, reads the data fromthe track. The access operation to write the data to or read the datafrom the track is performed on a sector by sector basis in principle.

The buffer controller 37 controls the data exchange of the buffer RAM 14to other functional blocks. The buffer controller 37 responds to theoperation from an unspecified sector position.

The disk formatter 36 in the first embodiment adopts the sector format(see FIG. 2) that contains relative position data indicating a relativeposition of the sector on the track, the body of data, and the ECC forthe entire sector area, or the sector format (see FIG. 3) that containsthe body of data and the ECC data for the entire sector containing therelative position of the sector.

In the former sector format, the sectors are provided with the relativeposition starting with the sector where the access operation has startedwhen the writing operation to the track is performed. The relativeposition and the ECC data based on the original write data aregenerated, and are recorded on the relative position field, the datafield, and the ECC field. Since the writing starts at the sector wherethe access operation has started, the search is not required. The readoperation starts at the sector where the access operation has started onthe target track. The storage location in the buffer RAM 14 isdetermined based on the sector position acquired from the relativeposition field. Even if the read operation starts at any sector, thedata stored on the track is reproduced in the buffer RAM 14 in theoriginal order. The magnetic head 22 is free from the search because themagnetic head 22 starts at any accessible start sector.

In the latter sector format, the sectors are provided with the relativeposition starting with the sector where the access operation has startedwhen the writing operation to the track is performed. The relativeposition and the ECC data based on the original write data aregenerated, and only both the record data and the ECC data are recordedon the sector. Since the writing starts at the sector where the accessoperation has started, the search is not required. The read operationstarts at the sector where the access operation has started on thetarget track. The error correction is performed using the ECC, and therelative position not written on to the sector is reproduced. Thestorage location in the buffer RAM 14 is determined based on therelative position. No matter where the read operation starts at anysector, the data stored on the track is reproduced in the buffer RAM 14in the original order. The magnetic head 22 is free from the search timebecause the magnetic head 22 starts at any accessible start sector.

The access operation starts at any sector regardless of whether thesector format shown in FIG. 2 or the sector format shown in FIG. 3 isused. The read and write operations start at any head positionimmediately subsequent to the seek operation, thereby eliminating thesearch time.

The disk formatter 36 in the first embodiment may adopt a track format(see FIG. 4) in which the sector has a fixed length with several sectorsstraddling the servo area, or a track format (see FIG. 5) in which thesector has a variable length with none of the sectors straddling theservo area.

In the former track format, the accessible start sector is a firstsector that is recorded without straddling the servo area after the seekoperation is performed to a target track. In the latter track format,the accessible start sector is a sector immediately subsequent to theservo area the magnetic head 22 has passed for the first time since theseek operation was performed to the target track. Regardless of any ofthe two track formats, the disk formatter 36 handles one track as a unitof access. The uncertain process of the read-ahead is eliminated, andthe seek start timing is reliably determined.

FIG. 9 illustrates an operational sequence of the disk formatter 13which writes data in the hard disk drive 10 in accordance with the firstembodiment of the present invention.

The host connected through the interface 17 is now assumed to transferdata subsequent to the issue of a write request command relating to acontent 1.

The host controller 33 transfers received data to the buffer controller37 while writing the conversion table (see Table 1) onto the buffer RAM14 to answer an access area to the requesting host.

The buffer controller 37 temporarily stores the transferred write datain the buffer RAM 14.

The ECC controller 35 generates a parity of the data temporarily storedin the buffer RAM 14, and rewrites the data onto the buffer RAM 14.

The buffer controller 37 successively reads the write data of one trackfrom the buffer RAM 14, and hands the write data over to the diskformatter 36. The disk formatter 36 writes the data on the sought trackon a track by track basis. The search time is not required because themagnetic head 22 starts writing from the accessible start sector on thesought track.

If the write data relating to the content 1 remains in the buffer RAM14, the ECC controller 35 reads next write data from the buffer RAM 14,generates a parity of the write data, and rewrites the write data to thebuffer RAM 14.

When the disk writing of the one track is complete, a write end noticeis issued to the buffer controller 37. In response, the buffercontroller 37 successively reads the write data of the one track fromthe buffer RAM 14, and hands the write data to the disk formatter 36.The disk formatter 36 performs the disk write operation on a track bytrack basis on the sought track (as already discussed). When the diskwriting of the one track is complete, a write end notice is issued tothe buffer controller 37.

When the process of writing the write data in the buffer RAM 14 iscomplete, the buffer controller 37 issues a notice to that effect to thehost controller 33. The buffer controller 37 updates the disk accessstate in response to the notice. The host may be notified of the end ofthe writing through the interface 17.

FIG. 10 illustrates an operational sequence of the disk formatter 13which writes data in the hard disk drive 10 in accordance with the firstembodiment of the present invention.

The host connected through the interface 17 is now assumed to issue aread request command relating to the content 1.

Upon receiving the read request command, the host controller 33 searchesthe conversion table (see Table 1), thereby retrieving the track numberand the head number of the content requested to read. The hostcontroller 33 instructs the disk formatter 36 to read the data from thecorresponding track.

After the magnetic head 22 seeks the designated track, the diskformatter 36 successively reads the data from the sector where theaccess operation has started on the track. The data reading is performedon a track by track basis. Since the read operation is performedstarting with the sector where the access operation has started, nosearch time is required.

The read data of the one track is transferred to the buffer controller37. The buffer controller 37 instructs the disk formatter 36 to read anext track.

The buffer controller 37 transfers the received read data to the ECCcontroller 35 for error correction. When the sector format shown in FIG.3 is adopted, the relative position of the sector is reproduced throughthe error correction. The buffer controller 37 expands, in the bufferRAM 14, the data of the sectors in accordance with the relativeposition, thereby reconstructing the data in the original order thereof.

The host controller 33 acquires the data, expanded and read in thebuffer RAM 14, through the buffer controller 37, and transfers the datato the requesting host through the interface 17.

In the first embodiment, the host designates the desired content withoutbeing conscious of the address of the seek destination when the hostrequests the hard disk drive 10 to read the data from or write the datato. The hard disk drive 10 manages the conversion table (see Table 1)that provides the correspondence between the content and the tracknumber, i.e., the seek destination. The track number as the seekdestination is acquired by the CPU 11 or the host controller 33.

FIG. 11 illustrates an operational sequence of the hard disk drive 10 inread and write operations, in which the CPU 11 acquires the track numberof the seek destination.

Upon receiving the read command from the host through the interface 17,the host controller 33 requests the CPU 11 to acquire the contentnumber.

The CPU 11 acquires the data of the conversion table, performing addressconversion in software operation, and thereby generating the tracknumber as the seek destination.

The CPU 11 requests the servo controller 16 to start a seek operation.The servo controller 16 controls power to the voice coil motor 23,thereby causing the head to perform the seek operation.

FIG. 12 illustrates an operational sequence of the hard disk drive 10 inread and write operations, in which the host controller 33 acquires thetrack number of the seek destination.

Upon receiving the read command from the host through the interface 17,the host controller 33 acquires the content number. The host controller33 acquires the data of the conversion table from the buffer controller37, performing the address conversion in hardware operations, andthereby acquiring the track number of the seek destination.

In succession, the host controller 33 requests the servo controller 16to start a seek operation. The servo controller 16 controls power to thevoice coil motor 23, thereby causing the head to perform the seekoperation.

FIG. 13 diagrammatically illustrates the structure of a storage area ofthe disk in accordance with a modification of the first embodiment ofthe present invention. As shown, the storage area of the magnetic disk21 is divided into a first storage area 21A and a second storage area21B.

In the first storage area 21A, the access operation is performed basedon the absolute addresses allocated beforehand, such as the cylindernumber (or the track number), the head number, and the sector number(CHS method).

In the second storage area 21B, the relative position addresses aresuccessively allocated to the sectors starting with the sector where theaccess operation has started on the track during the write access. Theaccess operation starts at the start sector that becomes accessible onthe track to access the one track (as already described).

In summary, the magnetic disk 21 shown in FIG. 13 is a hybrid-type harddisk in which the conventional access mode and the access mode of thepresent invention are mixed. By selectively using the recording areas,data of a large size with respect to the track (such as audio visualcontents) and other data (ordinary computer files) are efficientlywritten to or read from the disk.

B. Second Embodiment

As already described, the hard disk drive 10 of the first embodimentaccesses one track starting with the sector where the magnetic head 22is set to be on-track. More specifically, handling one track as a unitof access eliminates the need for the uncertain process of read-aheadand reliably determines the timing of the seek start. The accessoperation starts at any sector of one track, thereby eliminating thesearch time. The number of seeks is minimized, and the access time isreduced.

In the first embodiment of the present invention, the host can instructthe hard disk drive 10 to perform continuous accesses using simpleidentification information such as the content number identifying thecontent. In other words, the host does not use a LBA (logical blockaddress) used in a conventional file system in data accessing. The hostaccesses the disk without being conscious of a logical address space ata sector level such as the LBA. The hard disk drive 10 has difficulty inworking with (in assuring compatibility with) a host that uses aconventional file system.

In accordance with the second embodiment, the host accesses the diskusing the LBA as in the conventional art. Even when the LBA is used, onetrack is handled as a unit of access. The access operation starts at thesector where the magnetic head 22 is set to be on-track. In the same wayas the first embodiment, the second embodiment is free from theuncertain process of read-ahead, and the timing of the seek start isreliably determined. By accessing any sector of one track, the search iseliminated. The number of seeks is minimized, and the access time isreduced.

B-1. Allocation of the Logical Block Address

When data of a large size, such as video data, is continuously writtenon the medium, the access to the data is performed on a track by trackbasis in accordance with the present invention. Continuous access isconsidered to be effectively performed.

The continuous access refers to a series of accesses to record dataaccording to certain unit (a scene, a chapter, a constant time). Thedata is arranged using consecutive logical addresses, but the physicallocation thereof on the disk is not important. During the continuousaccess, differences in transmission rate with locations on the disk areaveraged, and the access operation is performed at a constanttransmission rate to the recording medium.

Since the host is not compatible with a large capacity disk in the CSHaddressing method, the LBA (Logical Block Address) mode is adopted.Logical serial numbers called LBA starting with 0, such as the cylindernumber, the head number, and the sector number, are used (as alreadydiscussed).

In ordinary disk drives, the logical block addresses are allocated tothe outermost track to inner tracks in the data area of the disk. FIG.28 illustrates the allocation of the logical block addresses to thetracks from the outermost track to the innermost track (two disks areemployed here). FIG. 29 illustrates the operation of the continuousaccess in which the logical block addresses are allocated to the tracksfrom the outermost track to the innermost track. As shown, when the readoperation or the write operation is completed on a target track, themagnetic head 22 is moved to a track having a continued logical blockaddress in the seek operation. As a result, a track skew correspondingto the seek time occurs.

If the zone bit recording method is adopted to make the recordingdensity on the tracks uniform, the transmission rate is graduallydegraded depending on the usage of the disk drive because the host(generally speaking, a file system) tends to use logical block addressesfrom small to large numbers.

The seek time for the magnetic head 22 to reach the target trackincreases with the seek distance. A rate of change in the seek timedepends on the seek distance. FIG. 14 illustrates the relationshipbetween the seek distance and the seek time. As shown, the rate ofincrease in the seek time decreases with the seek distance.

Before accessing a desired data area on the magnetic disk 21, it takes asearch time for the magnetic head 22 to arrive right below the targetsector subsequent to the seek operation of the magnetic head 22 to thetarget track. FIG. 30 illustrates the relationship between the skewingand the search time when the magnetic head 22 is shifted by four tracksin the seek operation.

In the second embodiment, the logical block addresses are allocated sothat the seek time covers a plurality of tracks of seek as long as theseek time does not exceed the search time. More specifically, the seekoperation not exceeding the mean search time is performed from the servoframe that has undergone the write operation of one track, and the timeused is referred to as a track skew.

The search time taking into consideration no skew is a reciprocal of thenumber of revolutions. The mean search time is half the search time.FIG. 15 plots the search time and the mean search time to the graphshown in FIG. 14.

The seek time is measured with the seek operation performed with theseek distance changed in the disk drive. The relationship between theseek distance not exceeding the search time or mean search time and theseek time determined from the seek distance is obtained. Based on theabove relationship, the following table is organized in the disk drive.Here, the seek time is represented by the number of servos (skews).

TABLE 2 Seek distance (tracks) 1-3 4-8 9-20 21-50 51-80 81-150 151-Skews 2 4 6 7 8 9 10 (number of servos)

When the data is written onto the magnetic disk 21, the consecutivelogical block addresses are arranged on the magnetic disk 21 taking intconsideration the track skews in Table 2. The data transfer speed isthus made uniform when the continuous access is performed across aplurality of tracks.

FIG. 16 illustrates the concept of the operation of continuous accesswherein the logical block address is allocated in accordance with thepresent invention (two disks are employed). As shown, during the writeoperation, the consecutive logical block addresses are successivelyallocated to the tracks within a range that the seek time or the trackskew does not exceed a predetermined value. If the head is positioned toany track in the seek operation, the seek time to the track during thecontinuous access is made uniform, and the search time is minimized.

B-2. Generation of the Logical Sector

When the magnetic head 22 passes the servo area presented on the datasurface of the magnetic disk 21 in the hard disk drive, whether or notthe magnetic head 22 is on-track is determined by integrating the signalfrom the servo pattern (as already discussed).

The start timing of the read and write operation to the magnetic disk 21is at the moment the magnetic head 22 passes over the servo area, andthe fast access may be achieved by performing the access operationimmediately subsequent to the passage of the magnetic head 22 over theservo area. The reading or writing is performed on one track, and thepassage of the head over the start servo area means that the magnetichead 22 has traveled by one full track. In response to the signal fromthe servo pattern, the on-track of the magnetic head 22 may berecognized. The seek to the next target track is performed by one servoearlier by verifying the on-track based on the servo pattern.

FIG. 31 illustrates an access operation in a conventional one trackseek. As shown, the start sector of the access is positioned taking intoconsideration the track skew determined from the seek time. This isfixed in the initialization of the disk drive at the manufacturing phasethereof. After the access to one track, the seek operation is performedto reach a next target track (often a track next to and immediatelyinside the first track). However, in the writing, the on-track checkmust be performed at the servo area present ahead of the access endsector. For this reason, one servo delay is caused at the longest.

The sectors on the track have logical block addresses (LBAs) andposition information of physical addresses such as CHS (cylinder, head,and sector). In the second embodiment, the combinations of the LBA andthe CHS are not singular, and are changed taking into consideration theindividual difference and the operational status of the disk drive. Aproper sector arrangement is thus achieved.

FIG. 17 illustrates an access operation in the seek of the track in thesecond embodiment of the present invention. As shown, it is assumed thata next target track is present on M tracks ahead after the end of theaccess to the one track (M is an integer equal to or larger than 1). Asalready discussed in section B-1, to achieve a uniform data transmissionspeed in the continuous access, the consecutive logical block addressesare successively allocated on the magnetic disk 21 taking intoconsideration the track skew. There are times when the next trackhappens to be located M tracks away rather than immediately inside thefirst track (see FIG. 16).

Referring to FIG. 17, the access start sector at the next target trackis a sector that is placed immediately subsequent to the servo area thatbecomes on-track. More specifically, this means that the track formatchanges due to a factor such as the seek distance from the immediatelyprior track during the writing.

The logical block addresses arranged on the track designate the range ofthe sector addresses present-on the one track and do not designate thephysical position of each sector. The logical block addresses of thetrack are determined by an endpoint of the track which was accessedimmediately before, and the tabled track skew (see Table 2).

FIG. 18 illustrates a sector range on the track and a start position ofa sector address wherein the sector arrangement is made on the track inaccordance with the present invention.

As shown, logical block addresses 2000 through 2499 are successivelyarranged along a circle in the track N which was accessed immediatelybefore. The next target track is determined as a track N+M, which isspaced by M tracks, by referencing the tabled track skew (see Table 2).

Logical block addresses 2500 through 2999 are allocated to sectors inthe track N+M, and the physical sector position of the start logicaladdress (2500) is a position shifted by a skew during the track seek ofthe M track.

B-3. Handling the Blank Area

In ordinary file formats, a storage space is managed with reference tothe LBA (Logical Block Address). The sectors are handled as a unit bypowers of 2 (eighth power, sixteenth power, 64th power to 2, forexample).

However, if the access is performed on a track by track basis in thesecond embodiment of the present invention, there are times when thenumber of sectors per track is not divisible by the unit of access witha remainder taking place.

An access method to the remainder sectors (hereinafter referred to as a“blank area”) will now be discussed.

The number of blank areas per track is the number of sectors per sectorminus one. The number of sectors per track is different from zone tozone.

Typical 3.5 inch hard disk drives (of the zone bit recording type) atthis writing in 2002 has about 1000 sectors at the outermost track, andabout 500 sectors at the innermost track. A maximum of 500 KB blankareas occurs.

Such blank areas correspond to 0.4 second at a rate of 10 Mbps in datasuch as video data which requires a real-time process. It is advisablethat the blank areas are assigned data, such as still pictures orordinary computer files, requiring no real-time handling.

When an access is made to request a continuous recording on the blankareas that fail to assure consecutive areas, the hard disk drive reportsthat the blank areas are not usable, and reports a start logical blockaddress on a next track.

B-3-1. Report and Host Process When No Continuous Accesses Can be Made

In response to a write access request from the host, he continuousaccess is not performed together with the immediately prior write accessprocess with the number of sectors to be processed not exceeding thenumber of sectors on one track. The process in such a case is performedas below.

If the immediately prior write process is already registered in thecache (the buffer RAM 14), if the write access request from the host hasan LBA continuous from a prior one, and if a one-track write processstarts together with immediately prior cache data, an continuous accessis possible.

If the number of sectors to be processed does not exceed the number ofsectors of the one track even with the write access request having thecontinuous LBA, the write process of the one track cannot be performedby a single cycle. Data already registered in the cache is written, andthe remainder becomes an empty area (a blank area).

An area expecting a next access is a sector in another track (track N+Min the following example). By reporting a start LBA to the host, thenext access is expected to start with that LBA.

FIG. 19 illustrates a write process performed in response to a writeaccess request not exceeding the number of sectors of one track. Asshown, the track N is a track on which a write process is performed.

In the second embodiment of the present invention, the accessing isperformed on a track by track basis. The write data is registered in thecache (the buffer RAM 14) until the number of sectors of data requestedto write reaches the number of sectors of one track, and the remainingsectors on the track are left as an area expecting an access from nowon.

If there is no access request from the host, the area expecting anaccess becomes a blank area. The file system of the host may registerthis blank area to place an access request to that area later.

Reported next to the host is another track (track N+M in FIG. 19) as anarea expecting a next access. The track N+M expecting an access,subsequent to the track N, is a track having an LBA continuous from thetrailing LBA of the track N.

B-3-2. Process in Non-continuous Access

The usage of the blank area is discussed which is generated when nocontinuous access is performed.

(1) Access Request of Small Data Other than Video Data

When the blank area is registered as an unused area in the file systemmanaged in the host, an access is performed on that area. When a writeaccess request for writing data of a small amount (still pictures orordinary computer files) other than the video data on the blank area isplaced, that request is received, and the process normally ends.

FIG. 20 illustrates the data write operation to the blank area. The filesystem in the host manages the unused area on the magnetic disk 21. Asshown, the host is assumed to issue the write access request to accessthe area registered in the file system as a blank area on the track N.Since the data to be written is as small in amount as data other thanthe video data, the hard disk drive writes the data starting at thebeginning of the blank area, and ends the process normally. The blankarea remaining subsequent to the write operation is newly registered inthe file system of the host.

FIG. 21 illustrates a flow of a process performed in response to a writeaccess request for non-continuous data of a small amount such as oneother than video data.

When a write access command (1) is issued from the host, the hard diskcontroller 13 receives the write access command through the interface17, and interrupts the CPU 11. In response, the CPU 11 performs acommand reception process.

When data is then transmitted from the host (2), the hard diskcontroller 13 receives the data through the interface 17, and interruptsthe CPU 11. In response, the CPU 11 performs a data reception process.

When an access to one track is not possible, the write data is stored inthe buffer RAM 14 as a cache. The hard disk controller 13 issues acommand end report (for normal ending) (1) to the host.

When a next write access command (2) is issued from the host, the harddisk controller 13 receives the next write access command (2) throughthe interface 17, and interrupts the CPU 11. In response, the CPU 11performs a command reception process. If the write access request is notcontinuous (i.e., not continuous from the LBA of the immediately priorwrite access), the hard disk controller 13 issues a command error report(2) to the host.

In response to the command error report from the hard disk drive, thehost issues the write access request (2′)=(2). The hard disk controller13 receives the write the write access request (2′) through theinterface 17, and interrupts the CPU 11. In response, the CPU 11performs a command reception process. Because of the write accessrequest of non-continuous data, the CPU 11 starts the disk formatter 36after the command reception process in response to the write accesscommand request. The hard disk controller 13 issues a command end report(2′) to the host.

In response to the start of the disk formatter 36, the hard diskcontroller 13 generates a parity and performs a data write operation onthe magnetic disk 21. Subsequent to the data writing, the hard diskcontroller 13 issues an interrupt to the CPU 11 again.

After the data reception process, the CPU 11 registers the write data inthe buffer RAM 14.

The hard disk controller 13 issues an interrupt to the CPU 11 againsubsequent to the write process to the magnetic disk 21. The CPU 11starts a seek operation and reports the result of the seek operation tothe hard disk controller 13.

(2) Access Request of Data of Large Amount Such as Video Data

When the blank area is registered as an unused area in the file systemmanaged in the host, an access is performed on that area (as alreadydiscussed).

When a write access request for writing data of a large amount such asvideo data is placed, that request is rejected at one time. The use ofthat area is expected at a next write access.

The host, compatible with the hard disk drive executing the aboveoperation, updates the designation of the LBA to the area expecting theaccess, and places a write access request again.

The host, incompatible with the hard disk drive executing the aboveoperation, repeats a write access request to the same LBA regardless ofthe report from the disk drive. The disk drive performs the accessoperation as requested by the host.

FIG. 22 illustrates a data write operation performed in response to awrite request for data of a large amount in a blank area.

The file system in the host manages the unused area in the magnetic disk21. Referring to FIG. 22, the host is assumed to issue a write access toan area registered in the file system as a blank area on the track N.Since the write access is intended to write data of a large amount suchas video data, the hard disk drive rejects the write request on theblank area on the track N. The hard disk drive then reports to the hostanother track (track N+M as shown) as an area expecting a next access.The track N+M expecting an access, subsequent to the track N, is a trackhaving an LBA continuous from the trailing LBA of the track N.

The host, compatible with the hard disk drive executing the aboveoperation, updates the designation of the LBA to the area expecting theaccess, and places a write access request again.

FIG. 23 illustrates a flow of a process of continuous accesses for dataof a large amount such as video data.

When a write access command (1) is issued from the host, the hard diskcontroller 13 receives the write access command through the interface17, and interrupts the CPU 11. In response, the CPU 11 performs acommand reception process.

When data is then transmitted from the host (1), the hard diskcontroller 13 receives the data through the interface 17, and interruptsthe CPU 11. In response, the CPU 11 performs a data reception process.

When an access to one track is not possible, the write data is stored inthe buffer RAM 14 as a cache. The hard disk controller 13 issues acommand end report (for normal ending) (1) to the host.

When the write access request and data transfer are performed in thecontinued LBA, the same registration in the cache is repeatedlyperformed as long as the amount of data registered in the buffer RAM 14fails to reach the access of one track.

When the amount of data registered in the buffer RAM 14 reaches theaccess of one track through the continued operation of the write accessrequest (2) and the data transfer (2) in the consecutive LBAs, the CPU11 starts the disk formatter 36 after the command reception processresponsive to the write access request command and the data receptionprocess responsive to the data transfer. The hard disk controller 13issues a command end report (for normal ending) (2) to the host.

The hard disk controller 13 generates a parity and executes a data writeoperation to the magnetic disk 21 in response to the start of the diskformatter 36. The hard disk controller 13 interrupts the CPU 11 againsubsequent to the end of the writing. The CPU 11 performs a seekoperation, and notifies the hard disk controller 13 of the result of theseek operation.

The CPU 11 determines in the above operational sequence whether or notthe access to one track is possible because the disk drive does notsupport the file system of the host. The access by the file system ofthe host may be used to check to see if the track falls within the rangeof access.

B-3-3. Operation of the Hard Disk Drive

The operation of the hard disk drive in the operational sequencesillustrated in FIGS. 21 and 23 is actually carried by the CPU 11 in thehard disk drive when the CPU 11 reads and executes micro codes stored inthe ROM 12, or by the hard disk controller 13 when the hard diskcontroller 13 executes a built-in logic.

The internal operation of the hard disk drive in the second embodimentwill now be discussed.

The hard disk drive performs the command reception process in responseto the write access request command from the host. In the commandreception process, the hard disk drive performs determination about thecontinuous access and the empty area (the blank area). If the cache datacurrently present in the buffer RAM 14 is effective, and if the requestrange of the received command indicates an LBA succeeding to thecommand, the access is determined as a continuous access.

FIG. 24 is a flow diagram of the command reception process on the harddisk drive.

The hard disk drive checks whether to perform a write with the cacheeffective (a write operation to the magnetic disk 21) (step S1).

If the cache is effective, the hard disk drive checks to see if therequest range of the received command indicates an LBA succeeding to thecache (step S2).

If the write request range is continuous from the cache, the hard diskdrive checks to see if the access range exceeds one track (step S3).

If the access range does not exceed one track, the hard disk driveregisters the data requested to write in the buffer RAM 14 as a cache(step S5), and ends the routine of the process. If the access rangeexceeds one track, the hard disk controller 13 sets the startup of thedisk formatter 36 (step S4), and ends the process routine.

If the hard disk drive determines that the cache is not effective, thehard disk controller 13 sets the startup of the disk formatter 36 (stepS9), performs a data write operation in the same way as a conventionalhard disk drive (see FIG. 20), and ends the process routine.

If the hard disk drive determines in step S2 that the request range ofthe received command indicates no continuous LBA, in other words,determines a non-continuous access, the hard disk drive checks whetherthe same write request is placed for the second time (step S6). If it isdetermined that the same write request is placed for the second time,the host is considered to be incompatible with the hard disk drive ofthe present invention. The hard disk controller 13 sets the startup ofthe disk formatter 36 (step S9), performs a data write operation in thesame way as a conventional hard disk drive (see FIG. 20), and ends theprocess routine.

If the same write request is not placed for the second time, the harddisk drive checks whether or not the write data falls within the rangeof the blank area (step S7). If it is determined that the write datafalls within the range of the blank area, the hard disk controller 13sets the startup of the disk formatter 36 (step S9), performs a datawrite operation in the same way as a conventional hard disk drive (seeFIG. 20), and ends the process routine.

If it is determined in step S7 that the write data does not fall withinthe range of the blank area, the hard disk drive reports to the host anarea expecting a next access (see FIG. 19 and FIG. 20) (step S8), andends the process routine.

The CPU 11 starts the seek operation in response to the generation ofthe parity and the end of the data write operation to the magnetic disk21. During the seek operation, the track skew table (see Table 2) isreferenced, and a physical position of a next access start sector isdetermined. The timing at which the data is written onto the disk fromthe start of the formatter is at the moment the access of one track inresponse to a next write request becomes possible. The seek time istypically predominant, and the data of one track is written subsequentto the seek operation. It is not necessary to prepare all data inadvance. It is sufficient that all data is prepared in the middle of thewrite operation.

FIG. 25 is a flow diagram of a seek operation.

The seek operation is started (step S11), and the physical position ofthe sector to be accessed next is calculated (step S12).

The physical position of the sector is determined by adding the servoarea number with which the access starts to the track skew table.

The physical position of the start sector is set in the hard diskcontroller 13 (step S13), and the process routine ends.

Appendix

The present invention has been discussed with reference to theparticular embodiments. It is obvious that those skilled in the artmodify and change the embodiments of the present invention withoutdeparting from the scope of the present invention. The embodiments ofthe present invention has been discussed for exemplary purposes only andare not intended to limit the scope of the present invention. The scopeof the present invention is solely determined by the appended claims.

INDUSTRIAL APPLICABILITY

The present invention provides an excellent data access controlapparatus, a data access control method, a controller, and a computerprogram for reducing an access time to a desired data storage location.

The present invention also provides an excellent data access controlapparatus, a data access control method, a controller, and a computerprogram, free from the generation of a search time and free from a delayin a seek startup due to a useless read-ahead operation.

The present invention provides an excellent data access controlapparatus, a data access control method, a controller, and a computerprogram, for reducing a seek time and a search time during a randomaccess by improving a data structure on a disk as a medium and a diskaccess method.

The present invention provides an excellent data access controlapparatus, a data access control method, a controller, and a computerprogram for making uniform the seek time of the track during thecontinuous access operation and minimizing the search time by allocatingthe logical block addresses to the sectors so that the seek time coversa plurality of track seeks within a range that the seek time does notexceed the search time.

The present invention provides an excellent data access controlapparatus, a data access control method, a controller, and a computerprogram for achieving an appropriate sector arrangement by changing thesector arrangement on the track depending on disk drive individualdifferences and a drive operational status.

1. A data access control apparatus for controlling access to a disk-typerecording medium that includes a plurality of substantially concentrictracks, with each track divided into a plurality of sectors, the controlapparatus comprising: seek means for seeking a target track; and dataaccess means for accessing the sectors of the target track in an orderthat is not based on a target sector or a predetermined sector location,but starts with a start sector that is the first sector that becomesphysically accessible to the data access means on the target track afterthe seeking of the target track is completed.
 2. A data access controlapparatus according to claim 1, wherein, during a write access, the dataaccess means successively allocates relative position addresses to thesectors on the track in the order starting with the sector where theaccess operation has started.
 3. A data access control apparatusaccording to claim 2, wherein, during a read access, the data accessmeans repositions data read from the sectors on the track in accordancewith the relative position addresses, thereby reproducing the writtendata.
 4. A data access control apparatus according to claim 2, furthercomprising error correction means which generates an error correctioncode for error correcting data and error corrects the data in accordancewith the error correction code, wherein, during a write access, the dataaccess means writes, on each sector, the relative position address, thebody of the data, and the error correction code which covers within anerror correction range thereof the relative position address, the databody, and the error code.
 5. A data access control apparatus accordingto claim 2, further comprising error correction means which generates anerror correction code for error correcting data and error corrects thedata in accordance with the error correction code, wherein, during awrite access, the data access means on each sector, the body of thedata, the relative position address, and the error correction code whichcovers within an error correction range thereof the data body, and theerror code.
 6. A data access control apparatus according to claim 5,wherein, during a read access, the data access means repositions thedata based on the relative position address into which the errorcorrection means error corrects the data read from each sector when thedata is reproduced.
 7. A data access control apparatus according toclaim 1, wherein servo areas are arranged at predetermined intervals onthe track, each sector has a fixed length, and each of several sectorsstraddles the servo area, and wherein the data access means treats, asan accessible start sector, a sector which is provided withoutstraddling the servo area on the target track.
 8. A data access controlapparatus according to claim 1, wherein servo areas are arranged atpredetermined intervals on the track, each sector has a variable length,and none of the sectors is designed to straddle the servo area, andwherein the data access means treats, as an accessible start sector, asector which is immediately subsequent to a servo area on the targettrack.
 9. A data access control apparatus according to claim 1, whereina zone bit recording method having the number of sectors per trackchanging with a radial position across the recording medium is adopted.10. A data access control apparatus according to claim 1, furthercomprising second data access means which accesses sectors in accordancewith absolute position addresses of a track and a sector, wherein thestorage area of the disk-type recording medium is divided into twopartitions, with one partition where the data access means accesses thesectors of the target track in the order starting with a start sectorthat becomes accessible and the other partition where the second dataaccess means accesses the sectors based on the absolute positionaddresses of the track and the sector.
 11. A data access controlapparatus for controlling access to a disk-type recording medium thatincludes a plurality of substantially concentric tracks, with each trackdivided into a plurality of sectors, the control apparatus comprising:seek means for seeking a target track; data access means for accessingthe sectors on the target track; determining means for determining arelationship between a seek time and a seek distance of the track to beaccessed by the data access means; and data write control means forallocating logical block addresses to the sectors during data writing sothat, even if the seek time includes a plurality of track seeks, theseek time does not exceed a search time, given the determinedrelationship between the seek time and the seek distance, wherein thesearch time is the time required to access a given sector on the targettrack after seeking of the track is completed.
 12. A data access controlapparatus according to claim 11, wherein the determining means fordetermining the relationship between the seek time and the seek distanceperforms a seek operation on a disk drive with the seek distancechanging, and measures the seek time thereby determining therelationship between the seek time and the seek distance.
 13. A dataaccess control apparatus for controlling access to a disk-type recordingmedium that includes a plurality of substantially concentric tracks,with each track divided into a plurality of sectors, the controlapparatus comprising: seek means for seeking a target track; data accessmeans for performing an access operation on the target track; and datawrite control means for treating, as an access start sector, a sectorimmediately subsequent to an on-track servo area during data writing.14. A data access control apparatus for controlling access to adisk-type recording medium that includes a plurality of substantiallyconcentric tracks, with each track divided into a plurality of sectors,the control apparatus comprising: seek means for seeking a target track;data access means for accessing the sectors of the target track in anorder that is not based on a target sector or a predetermined sectorlocation, but starts with a start sector that is the first sector thatbecomes physically accessible to the data access means on the targettrack after the seeking of the target track is completed; commandreceiving means for receiving a write request command; data receivingmeans for receiving write data; a cache which temporarily stores thereceived data; and data write control means for controlling a writeoperation of writing data onto the recording medium, wherein the datawrite control means causes the data access means to initiate a writeaccess of one track if the area of the data requested to write iscontinuous from the data stored in the cache, and if an access rangeexceeds one track.
 15. A data access control apparatus according toclaim 14, wherein the data write control means registers the datarequested to write in the cache if the area of the data requested towrite is continuous from the data stored in the cache, but if the accessrange does not exceed one track.
 16. A data access control apparatusaccording to claim 14, wherein the data write control means writes datain response to a second issue of the same write request command if thearea of the data requested to write is not continuous from the datastored in the cache.
 17. A data access control apparatus according toclaim 14, wherein the data write control means reports to a writerequesting source an area expecting a next access if the area of thedata requested to write is not continuous from the data stored in thecache and if write data fails to fall within the area of the datarequested to write.
 18. A data access control method for controllingaccess to a disk-type recording medium that includes a plurality ofsubstantially concentric tracks, with each track divided into aplurality of sectors, comprising: a seek step of seeking a target track;and a data access step of accessing the sectors of the target track inan order that is not based on a target sector or a predetermined sectorlocation, but starts with a start sector that is the first sector thatbecomes physically accessible to a data access means on the target trackafter the seeking of the target track is completed.
 19. A data accesscontrol method according to claim 18, wherein, during a write access,the data access step comprises successively allocating relative positionaddresses to the sectors on the track in the order starting with thesector where the access operation has started.
 20. A data access controlmethod according to claim 19, wherein, during a read access, the dataaccess step comprises repositioning data read from the sectors on thetrack in accordance with the relative position addresses to reproducethe written data.
 21. A data access control method according to claim19, further comprising an error code generating step of generating anerror correction code which covers the relative position address of thesector, the body of data, and the error correction code within an errorcorrection range, wherein, during a write access, the data access stepwrites, on each sector, the relative position address, the data body,and the error correction code.
 22. A data access control methodaccording to claim 19, further comprising an error code generating stepof generating an error correction code which covers the relativeposition address of the sector, the body of data, and the errorcorrection code within an error correction range, wherein, during awrite access, the data access step writes, on each sector, the databody, and the error correction code.
 23. A data access control methodaccording to claim 22, wherein, during a read access, the data accessstep comprises repositioning the data based on the relative positionaddress into which the error correction step corrects the data read fromeach sector when the data is reproduced.
 24. A data access controlmethod according to claim 18, wherein servo areas are arranged atpredetermined intervals on the track, each sector has a fixed length,and each of several sectors straddles the servo area, and wherein thedata access step comprises treating, as an accessible start sector, asector which is provided without straddling the servo area on the targettrack.
 25. A data access control method according to claim 18, whereinservo areas are arranged at predetermined intervals on the track, eachsector has a variable length, and none of the sectors is designed tostraddle the servo area, and wherein the data access step comprisestreating, as an accessible start sector, a sector which is immediatelysubsequent to a servo area on the target track.
 26. A data accesscontrol method according to claim 18, wherein a zone bit recordingmethod having the number of sectors per track changing with a radialposition across the recording medium is adopted.
 27. A data accesscontrol method according to claim 18, further comprising a second dataaccess step of accessing sectors in accordance with absolute positionaddresses of a track and a sector, wherein the storage area of thedisk-type recording medium is divided into two partitions, with onepartition where the data access step accesses the sectors of the targettrack in the order starting with a start sector that becomes accessibleand the other partition where the second data access step accesses thesectors based on the absolute position addresses of the track and thesector.
 28. A data access control method for controlling access to adisk-type recording medium that includes a plurality of substantiallyconcentric tracks, with each track divided into a plurality of sectors,comprising: a seek step of seeking a target track; a data access step ofaccessing the sectors of the target track; a determining step ofdetermining a relationship between a seek time and a seek distance ofthe track to be accessed in the data access step; and a data writecontrol step of allocating logical block addresses to the sectors duringdata writing so that, even if the seek time includes a plurality oftrack seeks, the seek time does not exceed a search time, given thedetermined relationship between the seek time and the seek distance,wherein the search time is the time required to access a given sector onthe target track after seeking of the track is completed.
 29. A dataaccess control method according to claim 28, wherein the determiningstep of determining the relationship between the seek time and the seekdistance comprises performing a seek operation on a disk drive with theseek distance changing, and measures the seek time to determine therelationship between the seek time and the seek distance.
 30. A dataaccess control method for controlling access to a disk-type recordingmedium that includes a plurality of substantially concentric tracks,with each track divided into a plurality of sectors, comprising: a seekstep of seeking a target track; a data access step of performing anaccess operation on the target track; and a data write control step oftreating, as an access start sector, a sector immediately subsequent toan on-track servo area during data writing.
 31. A data access controlmethod for controlling access to a disk-type recording medium thatincludes a plurality of substantially concentric tracks, with each trackdivided into a plurality of sectors, comprising: a seek step of seekinga target track; a data access step of accessing the sectors of thetarget track in an order that is not based on a target sector or apredetermined sector location, but starts with a start sector that isthe first sector that becomes physically accessible to a data accessmeans on the target track after the seeking of the target track iscompleted; a command receiving step of receiving a write requestcommand; a data receiving step of receiving write data; a storing stepof storing temporarily the received data in a cache; and a data writecontrol step of controlling a write operation of writing data onto therecording medium, wherein the data write control step comprisesinitiating a write access of one track if the area of the data requestedto write is continuous from the data stored in the cache, and if anaccess range exceeds one track.
 32. A data access control methodaccording to claim 31, wherein the data write control step comprisesregistering the data requested to write in the cache if the area of thedata requested to write is continuous from the data stored in the cache,but if the access range does not exceed one track.
 33. A data accesscontrol method according to claim 31, wherein the data write controlstep comprises writing data in response to a second issue of the samewrite request command if the area of the data requested to write is notcontinuous from the data stored in the cache.
 34. A data access controlmethod according to claim 31, wherein the data write control stepcomprises reporting to a write requesting source an area expecting anext access if the area of the data requested to write is not continuousfrom the data stored in the cache and if write data fails to fall withinthe area of the data requested to write.
 35. A controller forcontrolling an operation of a disk-type recording apparatus which seeksa track to access data on a data surface of a disk having a plurality ofsubstantially concentric tracks, with each track divided into aplurality of sectors, comprising: means for issuing a command to seek atarget track; and means for issuing a command to access the sectors ofthe target track in an order that is not based on a target sector or apredetermined sector location, but starts with a start sector that isthe first sector that becomes physically accessible to a data accessmeans on the target track after the seeking of the target track iscompleted.
 36. A controller for controlling an operation of a disk-typerecording apparatus which seeks a track to access data on a data surfaceof a disk having a plurality of substantially concentric tracks, witheach track divided into a plurality of sectors, comprising: means forissuing a command to seek a target track; means for issuing a command toaccess the data on the target track; means for determining arelationship between a seek distance and a seek time of the targettrack; and data write control means which allocates logical blockaddresses to the sectors during data writing so that, even if the seektime includes a plurality of track seeks, the seek time does not exceeda search time, given the determined relationship between the seek timeand the seek distance, wherein the search time is the time required toaccess a given sector on the target track after seeking of the track iscompleted.
 37. A controller for controlling an operation of a disk-typerecording apparatus which seeks a track to access data on a data surfaceof a disk having a plurality of substantially concentric tracks, witheach track divided into a plurality of sectors, comprising: means forissuing a command to seek a target track; means for issuing a command toaccess data on the target track; and data write control means whichtreats, as an access start sector, a sector immediately subsequent to anon-track servo area during data writing.
 38. A controller forcontrolling an operation of a disk-type recording apparatus which seeksa track to access data on a data surface of a disk having a plurality ofsubstantially concentric tracks, with each track divided into aplurality of sectors, comprising: seek means for seeking a target track;data access means for accessing the sectors of the target track in anorder that is not based on a target sector or a predetermined sectorlocation, but starts with a start sector that is the first sector thatbecomes physically accessible to the data access means on the targettrack after the seeking of the target track is completed; commandreceiving means which receives a write request command; data receivingmeans which receives write data; a cache which temporarily stores thereceived data; and means for issuing a write access command for onetrack if the area of the data requested to write is continuous from thedata stored in the cache, and if an access range exceeds one track. 39.A computer program embedded on a computer-readable medium and configuredto cause a computer system to control access to a disk-type recordingmedium that includes a plurality of substantially concentric tracks,with each track divided into a plurality of sectors, comprising: a seekstep of seeking a target track; and an access step of accessing sectorsof one track in an order that is not based on a target sector or apredetermined sector location, but starts with a start sector that isthe first sector that becomes physically accessible to a data accessmeans on the target track after the seeking of the target track iscompleted.
 40. A computer program embedded on a computer-readable mediumand configured to cause a computer system to control access to adisk-type recording medium that includes a plurality of substantiallyconcentric tracks, with each track divided into a plurality of sectors,comprising: a seek step of seeking a target track; an access step ofaccessing the data on the target track; a determining step ofdetermining a relationship between a seek distance and a seek time ofthe track; and a data write control step of allocating logical blockaddresses to the sectors during data writing so that, even if the seektime includes a plurality of track seeks, the seek time does not exceeda search time, given the determined relationship between the seek timeand the seek distance, wherein the search time is the time required toaccess a given sector on the target track after seeking of the track iscompleted.
 41. A computer program embedded on a computer-readable mediumand configured to cause a computer system to control access to adisk-type recording medium that includes a plurality of substantiallyconcentric tracks, with each track divided into a plurality of sectors,comprising: a seek step of seeking a target track; an access step ofaccessing data on the target track; and a data write control step oftreating, as an access start sector, a sector immediately subsequent toan on-track servo area during data writing.
 42. A computer programembedded on a computer-readable medium and configured to cause acomputer system to control access to a disk-type recording medium thatincludes a plurality of substantially concentric tracks, with each trackdivided into a plurality of sectors, comprising: a seek step of seekinga target track; a data access step of accessing the sectors of thetarget track in an order that is not based on a target sector or apredetermined sector location, but starts with a start sector that isthe first sector that becomes physically accessible to a data accessmeans on the target track after the seeking of the target track iscompleted; a command receiving step of receiving a write requestcommand; a data receiving step of receiving write data; a storing stepof temporarily storing the received data in a cache; and a data writecontrol step of controlling a write operation of writing data to therecording medium, wherein the data write control step comprises startinga write access command for one track if the area of the data requestedto write is continuous from the data stored in the cache, and if anaccess range exceeds one track.